/Engine/Source/Runtime/Engine/Classes/GameFramework/GameSession.h
Forcibly remove player from the server and ban them permanently
true if player was able to be banned, false otherwise
virtual bool BanPlayer ( [APlayerController](API\Runtime\Engine\GameFramework\APlayerController) * BannedPlayer, const [FText](API\Runtime\Core\Internationalization\FText) & BanReason )